1. Field of the Invention
This invention relates to a device for continuously mixing liquid and powder (hereinafter referred to as a continuous liquid-powder mixer). More specifically, this invention relates to a continuous liquid-powder mixer that is able to generate lower apparent viscosities for liquid-powder mixtures and in particular is highly adapted for the preparation of low-viscosity products in the area of compounds comprising the blends of powder fillers in liquid polymers such as liquid silicones.
2. Description of the Prior Art
Liquid silicone rubber compounds are employed in molding operations such as injection molding, compression molding, and the like, and are also used in various other operations as materials, such as moldmaking materials, architectural and building sealants. Liquid silicone rubber compounds are viscous mixtures of liquid silicone with a powder filler such as reinforcing silica. As is well known, lower apparent viscosities for these compounds provide a better processability in the aforementioned operations, while higher apparent viscosities impair the processability.
Liquid silicone rubber compounds with low apparent viscosities are prepared by mixing so as to give the highest possible dispersion of the powder filler that is being blended into the liquid silicone rubber. Compact devices that efficiently mix liquid and powder are disclosed in Japanese Patent Publication Numbers Sho 53-38828 [38,828/1978] and Hei 2-2610 [2,610/1990]. These are continuous mixers that contain a scraper-equipped rotating disk installed within a casing so as to divide the interior of the casing into upper and lower mixing compartments.
However, at high compounding ratios for microparticulate fillers such as fumed silica, i.e., at compounding ratios as high as approximately 10%, it is almost impossible using these prior-art devices to rapidly and inexpensively achieve an apparent viscosity for the compound (mixture) low enough to avoid negative consequences for the processability during molding.